Be a bit careful on what you read on the Internet regarding performance of either of the two. For some reason there is a lot of tribalism around people’s favorite DEs which leads to a lot of misinformation.

Gaming Performance is almost the same, just pick what works best for you: https://www.phoronix.com/review/kde-gnome-wayland21/4

Across all the games tested both native and titles via Steam Play (Proton + DXVK), the GNOME Wayland session most often was showing the best performance and across the wide range of tests carried out came to about 4% better performance than the GNOME X.Org session. The KDE Plasma Wayland session tended to perform slightly in front of its X.Org session as well for these Linux gaming tests but there were a few games still running into problems with the KDE Wayland session.

Yes. KDE is in fact much lighter and faster than GNOME. Apart from lower RAM usage, it taxes your CPU and GPU less.